1. Technical Field
The present disclosure relates to a printed circuit board.
2. Description of Related Art
Referring to FIGS. 3 and 4, some current printed circuit boards (PCBs) include a top layer 1, a bottom layer 2, a signal layer 3, and a ground layer 4. The top layer 1 and the bottom layer 2 are power layers. An electronic component 5 located on the top layer 1 is electrically connected to the top layer 1 and the bottom layer 2 through two vertical interconnect accesses (vias) 5a and 5b. Vias, such as 6a, 6b, 6c, 9a, 9b, and 9c are defined through the PCB, and are electrically connected to the top layer 1 and the bottom layer 2. A power supply 8 located on the top layer 1 is electrically connected to the top layer 1 and the bottom layer 2 through two vias 8a and 8b, to supply power to the electronic component 5. A part of the current from the power supply 8 flows to the electronic component 5 through the top layer 1. Another part of the current flows to the bottom layer 2 through the vias 8a, 8b, 6a, 6b, and 6c at first, then returns to the top layer 1 through the vias 9a, 9b, 9c, 5a, and 5b, thereby flowing to the electronic component 5 through the top layer 1. Because the current will flow to the electronic component 5 through a path with the least resistance, the current on the bottom layer 2 will flow to the top layer 1 through the via 9c which is the closest to the electronic component 5. As a result, if the current passing through the via 9c is too high, the resulting high temperature created may make the PCB unstable or may even damage the PCB.